1. The Field of the Invention
This invention relates to cannulation boards and, more particularly, to novel systems and methods for maintaining the wrist of a patient in an extended position for cannulation of a catheter and/or arterial blood sampling.
2. The Background Art
Invasive hemodynamic monitoring of cardiovascular function has become an integral and virtually routine aspect of intensive care units and operating rooms. One of the greatest values of hemodynamic monitoring is that it usually provides an improved understanding of the pathophysiology of the patient's current disorder and, in turn, often facilitates the making of a specific diagnosis. For this purpose, the information collected by means of hemodynamic monitoring may be used to guide the choice of initial therapy. After therapy is started, hemodynamic monitoring may be used to measure systemic blood pressure and direct transduction of the pressure waveform, whereby providing means for alerting caregivers as to physiological changes in the status of the patient and the effect of therapeutic intervention. Moreover, the measurements obtained by way of hemodynamic monitoring are typically useful in predicting prognosis.
Traditionally, invasive hemodynamic monitoring includes direct measurement of either the arterial pressure by means of an arterial cannula, central venous pressure by means of a central venous catheter, intracardiac pressures and flows by means of a pulmonary artery catheter, or by some combination of the three. The indications for using each of the foregoing modalities for invasive monitoring of cardiac status are usually determined by balancing the likelihood of obtaining useful information from a specific hemodynamic monitoring technique against the inherent risks and/or discomfort of the technique as realized by the patient.
Arterial pressure monitoring by means of an indwelling, peripheral arterial catheter is one of the most commonly used techniques of invasive hemodynamic monitoring. The general benefits of arterial pressure monitoring are: (1) continuous, precise, reproducible measurements of systolic, diastolic, and mean blood pressure; (2) accurate diagnosis of hemodynamic disorders characterized by fluctuations in blood pressure; (3) guidance in the choice of therapy for hypotension or hypertension; (4) continuous monitoring of the effect of therapy, allowing frequent adjustment of therapy for hypotension or hypertension; and (5) monitoring the patient's response to drug therapy. Another important benefit of an indwelling, peripheral arterial cannula is that it allows painless blood drawing from patients who would otherwise require multiple arterial and/or venous punctures for blood sampling. Incidently, an indwelling arterial catheter can add considerably to the comfort of such a patient by avoiding the pain and local injury associated with frequent arterial and/or venous punctures. In this regard, an arterial cannula may be placed more to optimize patient comfort than to monitor arterial blood pressure.
As readily appreciated by those skilled in the art, invasive arterial cannulation may be performed, for example, at the radial, ulnar, brachial, femoral, dorsalis pedis and axillary arteries. The radial artery is usually selected as the site for the placement of a peripheral arterial catheter due to its accessibility and the generally good collateral circulation supplied by the ulnar artery. Similarly, the radial artery is a good site for obtaining an arterial blood sample because it is superficially located and relatively easy to palpate and stabilize, is not adjacent to large veins and a probing needle should be relatively pain free as long as the periosteum of surrounding bone is avoided. Cannulation of the radial artery also seems to cause the least discomfort for patients since it allows considerable freedom of movement and typically does not require the immobilization of the joint. Further, the risk of ischemic injury to the hand and digits associated with radial artery catheterization is presumably low due to the presence of ample collateral circulation between the radial and ulnar arteries.
Although invasive, peripheral arterial cannulation can be performed reasonably safely in clinical settings, there is some risk of local infection, arterial occlusion and embolization. Consequently, cannulation is typically performed by personnel trained in such techniques or procedures. As appreciated by those skilled in the art, cannulation of a catheter in the radial artery or drawing an arterial blood sample from the radial artery at the wrist generally requires a patient's cooperation to extend the wrist during the cannulation procedure. This may require the aide of an assistant to maintain the wrist of the patient in an extended supine position or, in the alternative, the application of a means for hyperflexing the wrist of the patient in order to support an angle of extension whereby adequately exposing the radial artery for palpating and cannulation.
In accordance with one such prior art technique or method for cannulating a catheter in the radial artery, the wrist of a patient may be extended in a supine position by placing a towel or pillow under the wrist. In this manner, prior art radial cannulation methods generally provide a means for securing the wrist in relation to the towel or pillow by way of wrapping an adhesive tape around the towel or pillow and then around the hand, wrist and forearm of the patient one or more times to sustain a fixed relationship therebetween.
A significant disadvantage with prior art cannulation methods utilizing a towel or pillow to support the wrist of a patient in a supinated position readily embraces complications realized in attempting to support the wrist in an angle of extension suitable for adequately exposing the artery of the patient for cannulation or blood sampling. Moreover, prior art cannulation armboards or methods using adhesive tape to secure the hand, wrist and forearm of the patient to an armboard or cushioning means necessitates the removal of the portion of tape contacting the skin of the hand, wrist and forearm which inherently results in significant discomfort and probable pain upon its removal.
As technology progressed, prior art cannulation boards were developed by those skilled in the art comprising a cavity formed in the bottom of a flat, rigid armboard wherein a portion of the hand of a patient may be placed and a contoured wedge piece may be removably positioned adjacent the wrist joint to provide support for thrusting the wrist upward into an extended position. A serious disadvantage with prior art cannulation boards of this type is the general discomfort felt by the patient in relation to forcibly displacing the wrist joint into a hyperflexed position by means of a small rigid, contoured wedge piece.
To avoid the foregoing disadvantages in relation to the identifiable pain associated with removing adhesive tape from the skin of a patient and the inherent discomfort of forcibly thrusting a wrist joint upward into a hyperextended position, various other embodiments of cannulation boards were conceived by those skilled in the art in an attempt to alleviate the foregoing intrusions. For example, prior art cannulation boards were developed comprising multiple belts, straps, hook and loop fasteners, modified hook and loop fasteners or other conventional fastening means for retaining the hand, wrist and forearm of a patient in fixed relation to the cannulation board. One of such prior art cannulation boards consists of a flat, rectangular board having an upper surface including a fabric hook fastener removably interlocking with a fabric loop fastener formed on the bottom surface of a composite sheet. Disposed on the upper surface of the composite sheet is an adhesive covering which provides a means for rigidly securing the hand, wrist and forearm of the patient in relation thereto, thus becoming a single unit which can be easily removed and reattached to different armboards in various locations in a hospital, such as, for example, an operating room, recovery room, intensive care unit, etc.
A significant disadvantage to cannulation boards as disclosed above is their inability to provide a means for easily mounting or dismounting the hand, wrist and forearm from the cannulation board without having to manually release several restraining bands or straps or, in the alternative, without having to remove adhesive tape wrapping or an adhesive composite sheet from the skin of the patient's hand, wrist and forearm. In addition, prior art cannulation boards comprising multiple bands or straps are usually more difficult to clean and sterilize in view of the active bleeding that typically takes place from the site of needle penetration. For this reason, prior cannulation boards are generally discarded after initial utilization because of the potential contamination and, more especially, in view of passing infectious diseases to another patient. As will be further appreciated by those skilled in this particular art, economic considerations are significant when dealing with the highly competitive medical industry, since relatively complicated cannulation armboards comprising multiple working components (e.g., belts, straps, hook and loop fasteners, etc.) are frequently found to be commercially impractical. In this regard, even a slight savings in cost by way of reducing the number of working parts may substantially increase or enhance the commercial appeal of a particular cannulation board when considering relevant issues of its application or mass production.
Although prior art cannulation boards generally afford meaningful advantages over the use of towels or pillows, the overall effectiveness of such prior art cannulation boards has been frequently questioned in view of providing adequate and efficient means by which to expose the volar aspect of the wrist while preventing rotation of the hand, wrist and arm from its artificially supinated position in relation to the natural force acting on the hand, wrist and arm to pronate or rotate back into its neutral position.
Consistent with the foregoing and as illustrated by the number of prior art patents and other disclosures, efforts are continuously being made in an attempt to remedy the above-identified disadvantages. While prior art cannulation boards may appear generally suitable for their intended purpose, they nevertheless leave much to be desired from the standpoint of simplicity of construction, effectiveness of operation, functionality as to universal application and overall manufacturing costs. In this regard, the present invention provides for a novel wrist extending cannulation board and methods which overcome several deficiencies of cannulation boards of the prior art and resolves several problems left unsolved by known prior art.